Print error message if ImageSpace::Init fails.

Also changed some of the args in mem_map.cc to print as hex.

Bug: 13323732

Change-Id: I02cd81300793515d143e94473f48fc701e401b38
diff --git a/runtime/gc/space/image_space.cc b/runtime/gc/space/image_space.cc
index 8426fab..ca5b5a9 100644
--- a/runtime/gc/space/image_space.cc
+++ b/runtime/gc/space/image_space.cc
@@ -115,6 +115,8 @@
     space::ImageSpace* image_space = ImageSpace::Init(image_file_name.c_str(), true, &error_msg);
     if (image_space != nullptr) {
       return image_space;
+    } else {
+      LOG(WARNING) << error_msg;
     }
   }
   CHECK(GenerateImage(image_file_name, &error_msg))